The Coronary Drug Project (CDP) was undertaken to evaluate several lipid-lowering drugs in the long-term treatment of coronary heart disease and to study the natural history of this disease. The CDP is a multi-clinic study consisting of 53 Clinical Centers, a Coordinating Center, a Central laboratory, an EKG Reading Center, and a Drug Procurement and Distribution Center. 8,341 patients were enrolled in the study during recruitment from March '66 thru October '69. Only males between the ages of 30 and 64 having a history of at least one ECG-documented myocardial infarction and belonging to NYHA functional Class 1 to 11 were eligible for enrollment. Each patient was rabomly assigned to one of six treatment groups: mixed conjugated equine estrogens (2-dosage levels), clofibrate, dextrothyroxine, nicotinic acid, and placebo. All patients are to be followed for a minimum of 5- years on their assigned CDP medication plus a final 4-months off their CDP medication, unless definitive results allow termination before 5- years. The terminal 4-month period will end in February, 1975. Information from this study is being used to evaluate the CDP drugs with respect to mortality, cardiovascular morbidity and serum lipids, as well as side effects, biochemical effects and electrocardiographic changes. Placebo group data on the demographic, clinical electrocardiographic, biochemical, pharmacologic and radiographic variables observed at baseline as well as other aspects of the natural history of coronary heart disease will be analyzed for prognostic significance. The CDP was undertaken evaluate the use of acetylsalicylic acid in reducing the incidence of recurrent myocardial infarction and other cardiovascular events. Patients eligible for this study are CDP patients originally assigned to discontinued regimens.